Passive backplane architecture for master unit of distributed antenna system

ABSTRACT

One embodiment is directed to a distributed antenna system (DAS) for use with one or more base stations. The DAS comprises a plurality of remote antenna units, one or more donor units, and one or more transport units. The DAS is configured to communicatively couple each donor unit to at least one of the transport units and to communicatively couple each transport unit to at least one of the donor units. The DAS is configured so that all active downlink digital processing for producing the downlink transport signals transmitted from the transport units to the remote antenna units is performed by the donor units and the transport units. The DAS is configured so that all active uplink digital processing of the uplink transport signals received by the transport units from the remote antenna units is performed by the donor units and the transport units.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Pat. Application 17/033,013filed on Sep. 25, 2020, titled “PASSIVE BACKPLANE ARCHITECTURE FORMASTER UNIT OF DISTRIBUTED ANTENNA SYSTEM”, and U.S. Provisional Pat.Application Serial No. 62/906,602, filed on Sep. 26, 2019, same title,which are hereby incorporated herein by reference in its entirety.

BACKGROUND

A distributed antenna system (DAS) typically includes one or more masterunits that are communicatively coupled to a plurality of remote antennaunits. Each remote antenna unit can be coupled directly to one or moreof the master units or indirectly via one or more other remote antennaunits and/or via one or more intermediary or expansion units. A DAS istypically used to improve the coverage provided by one or more basestations that are coupled to the master units. These base stations canbe coupled to the master units via one or more cables or via a wirelessconnection, for example, using one or more donor antennas. The wirelessservice provided by the base stations can include commercial cellularservice and/or private or public safety wireless communications.

In general, each master unit receives one or more downlink signals fromone or more base stations and generates one or more downlink transportsignals derived from one or more of the received downlink base stationsignals. Each master unit transmits one or more downlink transportsignals to one or more of the remote antenna units. Each remote antennaunit typically serves one or more base stations coupled to the DAS. Eachremote antenna unit receives the downlink transport signals transmittedto it from one or more master units and uses the received downlinktransport signals to generate one or more downlink radio frequencysignals for the base stations it serves. The downlink radio frequencysignals are radiated from one or more coverage antennas associated withthat remote antenna unit. The downlink radio frequency signals areradiated for reception by user equipment. Typically, downlink signalsfor each base station are simulcast from multiple remote antenna unitsserving that base station. In this way, the DAS increases the coveragearea for the downlink capacity provided by the base stations.

Likewise, each remote antenna unit receives one or more uplink radiofrequency signals transmitted from the user equipment that iscommunicating with the base stations served by that remote antenna unit.Each remote antenna unit generates one or more uplink transport signalsderived from the one or more uplink radio frequency signals andtransmits them to one or more of the master units. Each master unitreceives the respective uplink transport signals transmitted to it fromone or more remote antenna units and uses the received uplink transportsignals to generate one or more uplink base station radio frequencysignals that are provided to the one or more base stations coupled tothat master unit. Typically, uplink signals received from the remoteantenna units serving each base station are combined or summed in orderto produce the base station signal provided to each base station. Inthis way, the DAS increases the coverage area for the uplink capacityprovided by the base stations.

FIG. 1 is a block diagram illustrating one way to implement a masterunit 100 of a DAS. In the example shown in FIG. 1 , digital transport isused in the DAS. The master unit 100 typically includes one or moredonor cards 102, one or more transport cards 104, and one or more activebackplanes 106. In this example, each active backplane 106 comprises aplurality of slots, where either a donor card 102 or a transport card104 can be inserted into each slot. Each active backplane 106 comprisesa field programmable gate array (FPGA) 108 that is configured toprocess, format, and route data communicated between the donor cards 102and transport cards 104. Also, each active backplane 106 comprises, foreach slot into which either a donor card 102 or transport card 104 canbe inserted, a respective backplane connector 110 that is used to couplethat card 102 or 104 to the FPGA 108. Each backplane connector 110, inthis example, includes multiple separate backplane channels 112 overwhich data can be separately communicated between the associated card102 or 104 and the FPGA 108. In this example, each backplane connector110 includes a respective backplane channel 112 for each externalinterface of the associated card 102 or 104 (that is, each base stationinterface 114 (described below) of a donor card 102 or each cableinterface 116 (described below) of a transport card 104).

In the example shown in FIG. 1 , each donor card 102 includes multiplebase station interfaces 114 that are used to couple the master unit 100(and the DAS more generally) to one or more base stations. In theexample shown in FIG. 1 , some of the donor cards 102 are configured tobe coupled to the external analog radio frequency (RF) interface of abase station that would otherwise be used to couple the base station toone or more antennas (if a DAS were not used). These donor cards arealso referred to here as “RF donor cards” 102. Also, in the exampleshown in FIG. 1 , some of the donor cards 102 are configured to becoupled to a digital baseband interface used for fronthaulcommunications between a baseband unit (BBU) and each remote radio head(RRH) of a base station. Examples of such digital baseband interfacesinclude, without limitation, digital baseband interfaces complying withthe Common Public Radio Interface (“CPRI”) protocol, the Enhanced CPRI(eCPRI) protocol, the Open Radio Access Network (O-RAN) protocol, theOpen Radio Equipment Interface (“ORI”) protocol, the Open Base StationStandard Initiative (“OBSAI”) protocol, or other protocol. These donorcards are also referred to here as “digital donor cards” 102.

In the example shown in FIG. 1 , each transport card 104 includesmultiple cable interfaces 116, each of which is used to couple themaster unit 100 to one or more remote antenna units of the DAS (eitherdirectly or indirectly via one or more other remote antenna units and/orvia one or more intermediary or expansion units). In the example shownin FIG. 1 , some of the transport cards 104 are configured tocommunicate over optical cables and these transport cards 104 are alsoreferred to here as “optical transport cards” 104. Also, in the exampleshown in FIG. 1 , some of transport cards 104 are configured tocommunicate over copper cables (for example, twisted-pair cables orcoaxial cables) and are also referred to here as “copper transportcards” 104. In this example, the copper transport cards 104 can also beconfigured to provide power to the remote antenna units (and anyexpansion units) over the copper cables (for example, usingPower-over-Ethernet (PoE) or direct current (DC) line-power techniques).

As noted above, each active backplane 106 comprises an FPGA 108 that isconfigured to process, format, and route data communicated between thedonor cards 102 and transport cards 104. For each base station interface114 of each RF donor card 102, the RF donor card 102 generates arespective stream of downlink digital samples from the analog downlinkRF signals received from the base station coupled to that base stationinterface 114. For each base station interface 114 of each digital donorcard 102, the digital donor card 102 terminates a respective stream ofdownlink digital samples received from a BBU of the base station coupledto that base station interface 114 via a digital baseband interface and,if necessary, converts (by re-sampling, synchronizing, combining,separating, gain adjusting, etc.) it into a stream of downlink digitalsamples compatible with the DAS. Each stream of downlink digital samplegenerated by a RF or digital donor card 102 is output to the FPGA 108 inthe active backplane 106 via a respective backplane channel 112 of thebackplane connector 110 to which that donor card 102 is connected. Foreach cable interface 116 of each transport card 104, the FPGA 108 of theactive backplane 106 multiplexes (frames) the streams of downlinkdigital samples for the base stations served by the set of remoteantenna units coupled to that cable interface 116 and outputs themultiplexed streams to that transport card 104 on the appropriatebackplane channel 112 of the backplane connector 110 used to connectthat transport card 104 to the active backplane 106. For each cableinterface 116 of each transport card 104, the transport card 104transmits the multiplexed streams of downlink digital samples to the setof remote antenna units coupled to that cable interface 116 via theattached cabling (and any intermediary devices).

For each cable interface 116 of each transport card 104, the transportcard 104 receives multiplexed streams of uplink digital samples from theset of remote antenna units coupled to that cable interface 116 andoutputs the multiplexed streams of uplink digital samples to the FPGA108 of the active backplane 106 on the appropriate backplane channel 112of the backplane connector 110 used connect that transport card 104 tothe active backplane 106. For each base station interface 114 of eachdonor card 102, the FPGA 108 extracts the individual streams of uplinkdigital samples generated by the various remote antenna units servingthe base station coupled to that base station interface 114, digitallysums the corresponding uplink digital samples from the various remoteantenna units, and outputs the stream of summed uplink digital samplesto the donor card 102 on the appropriate backplane channel 112 of thebackplane connector 110 used to connect that donor card 102 to theactive backplane 106. For each base station interface 114 of each RFdonor card 102, the RF donor card 102 generates an analog uplink RFsignal from the stream of summed uplink digital samples for the basestation coupled to that base station interface 114 and outputs theresulting analog uplink RF signal to that base station. For each basestation interface 114 of each digital donor card 102, the digital donorcard 102 receives the stream of summed uplink digital samples for thebase station coupled to that base station interface 114, if necessary,converts (by re-sampling, synchronizing, combining, separating, gainadjusting, etc.) it into a stream of uplink digital samples compatiblewith the digital baseband interface used by the BBU of the base stationcoupled to that digital donor card 102, and outputs the resulting streamof uplink digital samples to that BBU via the appropriate digitalbaseband interface.

In the example shown in FIG. 1 , the active backplane 106 compriseseight slots into which cards 102 or 104 can be inserted. In oneimplementation of this example, the active backplane 106 is implementedin a form that is two rack units (RUs) in size. If the DAS requires alarger number of cards 102 or 104, a larger capacity activity backplane106 can be used. FIG. 2 illustrates one example of an active backplane106 that is scaled to include sixteen slots into which cards 102 or 104can be inserted. In one implementation of this example, the activebackplane 106 is implemented in a form that is four rack units (RUs) insize. If the DAS requires more cards 102 or 104 than can be accommodatedby the largest capacity active backplane 106, two (or more) activebackplanes 106 can be interconnected with each other using transportcards 104.

FIG. 3 illustrates one example how two active backplanes 106 of the typeshown in FIG. 1 can be interconnected to each other in order to provideadditional capacity for cards 102 or 104 in a master unit 100. In thisexample, a transport card 104 inserted into a slot of a first activebackplane 106 is connected to a transport card 104 inserted into a slotof a second active backplane 106. These transport cards 104 areconnected to each other using optical cables connected to one or more ofthe cables interfaces 116 of those transport cards 104. These transportcards 104 are also referred to here as the “interconnect” transportcards 104. In the example shown in FIG. 3 , the interconnect transportcards 104 comprise optical transport cards 104; however, it is to beunderstood that copper transport cards 104 can also be used for theinterconnect transport cards 104. If one or more base stations connectedto the donor cards 102 of the first active backplane 106 need to beserved by one or more remote antenna units coupled to the transportcards 104 of the second active backplane 106, the FPGA 108 in the firstactive backplane 106 processes and then routes the corresponding streamsof digital samples for those base stations to and from the interconnecttransport card 104 of the first active backplane 106, which sends andreceives the streams of digital samples to the interconnect transportcard 104 of the second active backplane 106. The FPGA 108 in the secondactive backplane 106 processes and then routes the corresponding streamsof digital samples to and from the transport cards 104 of the secondactive backplane 106 that are coupled to the relevant remote antennaunits.

While the approach to implementing a modular master unit 100 for a DASillustrated in FIGS. 1-3 enables the number of donor cards 102 andtransport cards 104 to be scaled depending on the number of basestations and remote antenna units actually used, the FPGA 108 used ineach active backplane 106 must be provisioned with sufficient processingresources in order to support a configuration where cards 102 or 104 areinserted into all of the slots of the backplane 106. The FPGA 108 mustsupport this maximum configuration even though in many real-wordconfigurations cards 102 or 104 are not actually inserted into all ofthe slots of the backplane 106. As a result, the cost and processingpower of the FPGA 108 in each active backplane 106 does not scale withthe size of the DAS.

SUMMARY

One embodiment is directed to a master unit for a distributed antennasystem (DAS) that also includes a plurality of remote antenna units.Each remote antenna unit serves one or more base stations. The masterunit comprises one or more donor cards. Each donor card is configured tocouple that donor card to at least one base station. The master unitfurther comprises one or more transport cards. Each transport card isconfigured to couple that transport card to one or more sets of remoteantenna units. The master unit further comprises at least one passivebackplane. Each passive backplane comprises a plurality of backplaneconnectors. Each of the backplane connectors is configured to connect arespective donor card or transport card to that passive backplane. Eachof the backplane connectors is connected to each of the other connectorsvia one or more respective passive bi-directional backplane channels.The master unit is configured so that all active processing of streamsof digital samples transported via the DAS is performed by the donorcards and transport cards and not the passive backplane.

Another embodiment is directed to a distributed antenna system (DAS)comprising a master unit coupled to one or more base stations and aplurality of remote antenna units. Each remote antenna unit serves oneor more of the base stations. The master unit comprises one or moredonor cards. Each donor card is configured to couple that donor card toat least one base station. The master unit further comprises one or moretransport cards. Each transport card is configured to couple thattransport card to one or more sets of remote antenna units. The masterunit further comprises at least one passive backplane. Each passivebackplane comprises a plurality of backplane connectors. Each of thebackplane connectors is configured to connect a respective donor card ortransport card to that passive backplane. Each of the backplaneconnectors is connected to each of the other connectors via one or morerespective passive bi-directional backplane channels. The master unit isconfigured so that all active processing of streams of digital samplestransported via the DAS is performed by the donor cards and transportcards and not the passive backplane.

Other embodiments are disclosed.

The details of various embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbecome apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating one way to implement a masterunit of a distributed antenna system.

FIG. 2 illustrates one example of an active backplane that is scaled toinclude sixteen slots into which cards can be inserted.

FIG. 3 illustrates one example how two active backplanes of the typeshown in FIG. 1 can be interconnected to each other in order to provideadditional capacity for cards in a master unit.

FIG. 4 is a block diagram illustrating one exemplary embodiment of adistributed antenna system in which the passive backplane described herecan be used.

FIG. 5 is a block diagram illustrating one exemplary embodiment of themaster unit of FIG. 4 .

FIG. 6 illustrates one example of two passive backplanes that areconnected to each other via their expansion ports in order to form alarger capacity passive backplane assembly.

FIG. 7 illustrates a second example of two passive backplanes that areconnected to each other via their expansion ports in order to form alarger capacity passive backplane assembly.

FIG. 8 illustrates one example of two passive backplanes that areconnected to each other via transport cards inserted into the backplanesin order to form a larger capacity passive backplane assembly.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 4 is a block diagram illustrating one exemplary embodiment of adistributed antenna system 400 in which the passive backplane describedhere can be used.

The DAS 400 comprises one or more master units 402 that arecommunicatively coupled to one or more remote antenna units 404 via oneor more cables 406. Each remote antenna unit 404 can be communicativelycoupled directly to one or more of the master units 402 or indirectlyvia one or more other remote antenna units 404 and/or via one or moreexpansion (or other intermediary) units 408.

Each master unit 402 is communicatively coupled to one or more basestations 410. For example, each master unit 402 can be coupled to atleast some of the base stations 410 via an external analog radiofrequency (RF) interface of the base stations 410 that would otherwisebe used to couple each base station 410 to one or more antennas (if aDAS were not used). Also, each master unit 402 can also be coupled to atleast some of the base stations 410 via a digital baseband interfaceused for fronthaul communications between a BBU and each RRH of a basestation. Examples of such digital baseband interfaces include, withoutlimitation, digital baseband interfaces complying with the CPRIprotocol, the eCPRI protocol, the O-RAN protocol, the ORI protocol, theOBSAI protocol, or other protocol. In the exemplary embodiment shown inFIG. 4 , each master unit 402 is coupled to one or more base stations410 via one or more cables. In other embodiments, each master unit 402can be coupled to the base stations 410 in other ways (for example,wirelessly using one or more donor antennas).

The base stations 410 can also be coupled to the master units 402 usinga network of attenuators, combiners, splitters, amplifiers, filters,cross-connects, etc., (sometimes referred to collectively as a“point-of-interface” or “POI”). This network can be included in themaster units 402 and/or can be separate from the master units 402. Thisnetwork can be used so that, in the downlink, the desired set of RFchannels output by the base stations 410 can be extracted, combined, androuted to the appropriate master units 402, and so that, in the uplink,the desired set of carriers output by the master units 402 can beextracted, combined, and routed to the appropriate interface of eachbase station 410. It is to be understood, however, that this is oneexample and that other embodiments can be implemented in other ways.

In general, each master unit 402 receives one or more downlink basestation signals from one or more base stations 410 and generates one ormore downlink transport signals derived from one or more of the receiveddownlink base station signals. Each master unit 402 transmits one ormore downlink transport signals to one or more of the remote antennaunits 404. Each remote antenna unit 404 typically serves one or morebase stations 410 coupled to the DAS 400. Each remote antenna unit 404receives the downlink transport signals transmitted to it from one ormore master units 402 and uses the received downlink transport signalsto generate one or more downlink radio frequency signals for the basestations 410 it serves. The downlink radio frequency signals areradiated from one or more coverage antennas 412 associated with thatremote antenna unit 404. The downlink radio frequency signals areradiated for reception by user equipment 414. Typically, downlinksignals for each base station 410 are simulcast from multiple remoteantenna units 404 serving that base station 410. In this way, the DAS400 increases the coverage area for the downlink capacity provided bythe base stations 410.

Likewise, each remote antenna unit 404 receives one or more uplink radiofrequency signals transmitted from user equipment 414 communicating withthe base stations 410 served by that remote antenna unit 404. Eachremote antenna unit 404 generates one or more uplink transport signalsderived from the one or more uplink radio frequency signals andtransmits them to one or more of the master units 402. Each master unit402 receives the respective uplink transport signals transmitted to itfrom one or more remote antenna units 404 and uses the received uplinktransport signals to generate one or more uplink base station signalsthat are provided to the one or more base stations 410 coupled to thatmaster unit 402. Typically, uplink signals received from multiple remoteantenna units 404 serving each base station are combined or summed inorder to produce the base station signal provided to that base station410. In this way, the DAS 400 increases the coverage area for the uplinkcapacity provided by the base stations 410.

In this example, the DAS 400 uses digital transport.

FIG. 5 is a block diagram illustrating one exemplary embodiment of themaster unit 402 of FIG. 4 .

The master unit 402 includes one or more donor cards 416, one or moretransport cards 418, and a passive backplane 420. The passive backplane420 comprises a plurality of slots, where either a donor card 416 or atransport card 418 can be inserted into each slot depending on the needsof that particular DAS 400 implementation.

Each passive backplane 420 comprises, for each slot into which either adonor card 416 or transport card 418 can be inserted, a respectivebackplane connector 422 that is used to couple that card 416 or 418 tothe passive backplane 420. Each passive backplane 420 also comprises anexpansion port 424 that is used for coupling that passive backplane 420to the expansion port 424 of another passive backplane 420.

Each passive backplane 420 comprises one or more separate high-speed,passive, bi-directional backplane channels 426 between each backplaneconnector 422 and each other backplane connector 422 and the expansionport 424. Only some of the backplane channels 426 are shown in FIG. 5for ease of illustration. In the example shown in FIG. 5 , the passivebackplane 420 comprises eight slots into which donor cards 416 ortransport cards 418 can be inserted and one expansion port 424.Therefore, in this example, each backplane connector 422 is connected tothe other seven backplane connectors 422 and the one expansion port 424via one or more respective passive, high-speed, bi-directional backplanechannels 426.

In the example shown in FIG. 5 , each donor card 416 includes multiplebase station interfaces 428 that are used to couple the master unit 402(and the DAS 400 more generally) to one or more base stations 410. Eachdonor card 416 (among other things) is configured to generate one ormore streams of digital samples from one or more downlink base stationsignals received from each base station 410 coupled to that donor card416 and to generate one or more uplink base station signals from one ormore uplink streams of digital samples, where the uplink base stationsignals are communicated to the base stations 410.

In the example shown in FIG. 5 , some of the donor cards 416 areconfigured to be coupled to the external analog radio frequency (RF)interface of a base station 410. The external analog RF interface is theinterface that would otherwise be used to couple the base station 420 toone or more antennas (if a DAS were not used). These donor cards 416 arealso referred to here as “RF donor cards” 416. For the RF donor cards416, the downlink and uplink base station signals comprise analogdownlink and uplink RF signals.

Also, in the example shown in FIG. 5 , some of the donor cards 416 areconfigured to be coupled to a baseband unit of a base station 410 usingthe digital baseband interface used for fronthaul communications betweena BBU and each RRH. Examples of such digital baseband interfacesinclude, without limitation, digital baseband interfaces complying withthe CPRI protocol, the eCPRI protocol, the O-RAN protocol, the ORIprotocol, the OBSAI protocol, or other protocol. These donor cards 416are also referred to here as “digital donor cards” 416. For the digitaldonor cards 416, the downlink and uplink base station signals comprisedownlink and uplink digital baseband data (for example, downlink anduplink digital CPRI, eCPRI, O-RAN, ORI, or OBSAl baseband data).

In the example shown in FIG. 5 , each transport card 418 includesmultiple cable interfaces 430, each of which is used to couple themaster unit 402 to one or more remote antenna units 404 of the DAS 400(either directly or indirectly via one or more other remote antennaunits 404 and/or via one or more intermediary or expansion units 408).In the example shown in FIG. 5 , some of the transport cards 418 areconfigured to communicate over optical cables and these transport cards418 are also referred to here as “optical transport cards” 418. Also, inthe example shown in FIG. 5 , some of the transport cards 418 areconfigured to communicate over copper cables (for example, twisted-paircables or coaxial cables) and are also referred to here as “coppertransport cards” 418. In this example, the copper transport cards 418can also be configured to provide power to the remote antenna units 404(and expansion units 408) over the copper cables (for example, usingPower-over-Ethernet (PoE) or direct current (DC) line-power techniques).

In this example, each passive backplane 420 comprises a dedicated slot(not shown) into which a system user interface card (not shown) can beinserted. The system user interface card is configured to implement amanagement interface for the DAS 400 and the cards 416 and 418 insertedtherein. The passive backplane 420 is configured to couple eachbackplane connector 422 (and any card 416 or 418 connected thereto) tothe system user interface card. The system user interface card alsocomprises one or more Ethernet interfaces via which external devices orsystems can be coupled to the system user interface card in order tocommunicate with the management interface implemented for the DAS 400.

As noted above, in the example shown in FIG. 5 , the backplane 420comprises a passive backplane. The master unit 402 is configured so thatall active processing of the digital samples transported via the DAS 400is performed by the donor cards 416 and transport cards 418 and not thepassive backplane 420. That is, the active processing of streams ofdigital samples that would be performed by the FPGA 108 of the activebackplane 106 described above in connection with FIGS. 1-3 is notperformed by the backplane 420 in the example shown in FIG. 5 butinstead is performed in either the donor cards 416 or the transportcards 418.

In the example shown in FIG. 5 , each RF donor card 416 comprises an RFfront end 450, processing system 452, and input/output (I/O)transceivers 454, and each digital donor card 416 comprises one or moredigital baseband interface devices 451 (for example, implemented using achip set suitable for the digital baseband interface that includes,without limitation, a physical layer device (PHY) and media accesscontrol (MAC) device for that digital baseband interface), processingsystem 452, and input/output (I/O) transceivers 454. Also, In theexample shown in FIG. 5 , each transport card 418 comprises input/output(I/O) transceivers 456, processing system 458, and cable transceivers460. Each donor card 416 and transport card 418 (and the componentsthereof) can be implemented at least in part using an FPGA and/or asystem-on-chip (SOC).

As noted above, each donor card 416 is configured to generate one ormore streams of digital samples from one or more downlink base stationsignals received from each base station 410 coupled to that donor card416. In the example shown in FIG. 5 where the donor cards 416 compriseRF donor cards 416, the RF front end 450, for each base stationinterface 428, generates one or more streams of downlink digital samplesfrom the one or more analog downlink RF signals received from the basestation 410 coupled to that base station interface 428. In oneimplementation, these streams of downlink digital samples comprisedigital in-phase and quadrature (IQ) samples. Also, in thisimplementation, the RF front-end 450 comprises, for each base stationinterface 428, a mixer to down-convert the analog downlink RF signalsreceived from the base station 410 coupled to that base stationinterface 428 to an analog intermediate frequency (IF) signal, ananalog-to-digital converter to digitize the analog IF signal in order toproduce real downlink digital samples, and a digital downconverter (DDC)to digitally down-convert the real downlink digital samples to producedownlink digital in-phase and quadrature (IQ) samples. The resultingstreams of downlink digital IQ samples for each base station interface428 are provided to the processing system 452. The processing system452, for each transport card 418 that is coupled to one or more remoteantenna units 404 that serve one or more of the base stations 410coupled to the associated donor card 416, multiplexes (frames) thestreams of downlink digital IQ samples for those base stations 410, andoutputs the multiplexed streams to the I/O transceivers 454. The I/Otransceivers 454 communicate each set of multiplexed downlink streams onan appropriate backplane channel 426 of the backplane connector 422 usedto connect that donor card 416 to the passive backplane 420. The I/Otransceivers 454 communicate each set of multiplexed downlink streamsover the passive backplane 420 to an appropriate transport card 418 orexpansion port 424.

In the example shown in FIG. 5 where the donor cards 416 comprisedigital donor cards 416, the one or more digital baseband interfacedevices 451, for each base station interface 428, terminate a respectivestream of downlink digital samples received from a BBU of the basestation coupled to that base station interface 428 via a digitalbaseband interface and provides the respective stream of downlinkdigital samples to the processing system 452 in that digital donor card416. The processing system 452, if necessary, converts (by re-sampling,synchronizing, combining, separating, gain adjusting, etc.) therespective stream of downlink digital samples into a stream of downlinkdigital samples compatible with the DAS 400 and otherwise multiplexesand outputs the various streams of downlink digital samples as describedabove in connection with the RF donor card 416.

The I/O transceivers 456 in each transport card 418 are used to receivemultiplexed streams of downlink digital IQ samples communicated to itfrom the various donor cards 416 via the respective backplane channels426 of the backplane connector 422 used to connect that transport card418 to the passive backplane 420. The processing system 458 in eachtransport card 418 extracts the individual streams of downlink digitalsamples from the received multiplexed streams of downlink digitalsamples. For each cable interface 430 of the transport card 418, theprocessing system 458 in the transport card 418 multiplexes (frames) thestreams of downlink digital samples for the base stations 410 served bythe remote antenna units 404 that are coupled to that cable interface430 and a respective cable transceiver 460 in the transport card 418transmits the set of multiplexed streams of downlink digital samples tothe remote antenna units that are coupled to that cable interface 430via the attached cables 406 (shown in FIG. 4 ) (and any intermediarydevices).

The cable transceivers 460 of each transport card 418 receivemultiplexed streams of uplink digital samples communicated to thetransport card 418 from the various remote antenna units 404 coupled tothe various cable interfaces 430 of that transport card 428. Theprocessing system 458 in each transport card 418 extracts the individualstreams of uplink digital samples from the received multiplexed streamsof uplink digital samples. For each such base station 410 for which thetransport card 418 has received streams of uplink digital samples frommultiple remote antenna units 404, the processing system 458 in thetransport card 418 digitally sums the extracted streams of uplinkdigital signals for that base station 410. For each donor card 416 thatis coupled to one or more base stations 410 served by one or more of theremote antenna units 404 coupled to a given transport card 418, theprocessing system 458 in that transport card 418 multiplexes (frames)the streams of summed uplink digital samples for those base stations 410and the respective I/O transceiver 456 in that transport card 418outputs the set of multiplexed streams to that donor card 416 on theappropriate backplane channel 426 of the backplane connector 422 used toconnect that transport card 418 to the passive backplane 420.

The I/O transceivers 454 in each donor card 416 receive multiplexedstreams of summed uplink digital samples communicated to it from thevarious transport cards 418 via the respective backplane channels 426 ofthe backplane connector 422 used to connect that donor card 416 to thepassive backplane 420. The processing system 452 in each donor card 416extracts the individual streams of summed uplink digital samples fromthe received multiplexed streams of summed uplink digital samples. Foreach such base station 410 for which the donor card 416 has receivedstreams of uplink digital samples from multiple transport cards 418, theprocessing system 458 in the donor card 416 digitally sums the extractedstreams of summed uplink digital signals for the base station 410.

As noted above, each donor card 416 is configured to generate one ormore uplink base station signals from one or more uplink streams ofdigital samples, where the uplink base station signals are communicatedto the base stations 410. In the example shown in FIG. 5 where the donorcards 416 comprise RF donor cards 416, the RF front end 450, for eachbase station interface 428 of the RF donor card 416, generates arespective one or more analog uplink RF signals from the one or morestreams of summed uplink digital samples output by the processing system452 for the base station 410 coupled to that base station interface 428and provides the analog uplink RF signal to that base station 410. Inone implementation, the RF front end 450 comprises, for each basestation interface 428, a digital upconverter (DUC) configured todigitally up-convert each stream of summed uplink digital IQ samplesoutput by the processing system 452 in order to produce real uplinkdigital samples, a digital-to-analog converter in order to produce ananalog uplink IF signal from the real uplink digital samples, and amixer in order to up-convert the analog uplink IF signal to RF in orderto produce each analog uplink RF signal that is provided to the basestation 410 coupled to that base station interface 428.

In the example shown in FIG. 5 where the donor cards 416 comprisedigital donor cards 416, the processing system 452 in each digital donorcard 416 receives, extracts, and digitally sums the streams of summeduplink digital samples as described above in connection with the RFdonor card 416 and, if necessary, converts (by re-sampling,synchronizing, combining, separating, gain adjusting, etc.) them intostreams of uplink digital samples compatible with the digital basebandinterface used by the BBUs of the base stations 410 coupled to thatdigital donor card 416. The one or more digital baseband interfacedevices 451, for each base station interface 428 of each digital donorcard 416, communicate, to the BBU of the base station 410 coupled tothat base station interface 428 using the appropriate digital basebandinterface, the stream of summed uplink digital samples generated by theprocessing system 452.

In the example shown in FIG. 5 , the passive backplane 420 compriseseight slots into which cards 416 or 418 can be inserted. If the DAS 400requires a larger number of cards 416 or 418, two passive backplanes 420can be connected to each other via their expansion ports 424 in order toform a larger capacity passive backplane assembly.

FIG. 6 illustrates one example of two passive backplanes 420 that areconnected to each other via their expansion ports 424 in order to form alarger capacity passive backplane assembly. In this example, theexpansion ports 424 of each passive backplane 420 are connected to eachother using appropriate board-to-board connectors. In the example shownin FIG. 6 , one of the passive backplanes 420 comprises a high-speedswitching matrix 434. The high-speed switching matrix 434 is configuredto couple any backplane channel 426 of the expansion port 424 of a firstpassive backplane 420 to a single backplane channel 426 of the expansionport 424 of a second passive backplane 420. In this example, the firstpassive backplane 420 is configured to couple the high-speed switchingmatrix 434 to the system user interface card. The high-speed switchingmatrix 434 can be configured via the management interface implemented bythe system user interface card. The high-speed switching matrix 434 cancouple any donor card 416 inserted into a slot of one passive backplane420 to any single transport card 418 inserted into a slot of the otherpassive backplane 420.

FIG. 7 illustrates a second example of two passive backplanes 420 thatare connected to each other via their expansion ports 424 in order toform a larger capacity passive backplane assembly. The example shown inFIG. 7 is the same as the example shown in FIG. 6 , except that thehigh-speed switch matrix 434 is mounted to a printed circuit board (PCB)436 that is separate from the PCBs used to implement the two passivebackplanes 420. In this example, matrix PCB 436 is connected to theexpansion ports 424 of each passive backplane 420 using appropriateboard-to-board connectors. In this example, the high-speed switch matrix434 (and the associated matrix PCB 436) need only be deployed if neededto connect two passive backplanes 420 to each other via their expansionports 424 in order to form a larger capacity passive backplane assembly.If that is not the case, the high-speed switch matrix 434 (and theassociated matrix PCB 436) need not be deployed, thereby avoiding thecost associated therewith.

FIG. 8 illustrates one example of two passive backplanes 420 that areconnected to each other via transport cards 418 inserted into thebackplanes 420 in order to form a larger capacity passive backplaneassembly. In this example, a transport card 418 inserted into a slot ofa first passive backplane 420 is connected to a transport card 418inserted into a slot of a second passive backplane 420 using opticalcables connected to one or more of the cables interfaces 430 of thosetransport cards 418. These transport cards 418 are also referred to hereas the “interconnect” transport cards 418. If one or more base stations410 connected to the donor cards 416 of the first passive backplane 420need to be served by one or more remote antenna units 404 coupled to thetransport cards 418 of the second passive backplane 420, theinterconnect transport card 418 of the first passive backplane 420receives the corresponding streams of downlink digital samples for thosebase stations 410 from the appropriate donor cards 416 of the firstpassive backplane 420 and sends them to the interconnect transport card418 of the second passive backplane 420, which sends the streams ofdownlink digital samples to the appropriate transport cards 418 of thesecond passive backplane 420. The interconnect transport card 418 in thesecond passive backplane 420 receives the corresponding streams ofuplink digital samples from the appropriate transport card 418 of thesecond passive backplane 420 and sends them to the interconnecttransport card 418 of the first passive backplane 420, which sends thestreams of uplink digital samples to the appropriate donor cards 416 ofthe first passive backplane 420. Multiple transport cards 418 of each ofthe passive backplanes 420 can be used as interconnect transport cards418 if necessary (depending on the amount of interconnect bandwidth thatis needed).

While the approach shown in FIG. 8 provides a mechanism to connect twopassive backplanes 420 to each other in order to form a larger capacitypassive backplane assembly, this approach does so at the expense oflosing the use of the slots in which the interconnect transport cards418 are inserted.

The approach shown in FIG. 8 can also be combined with the approachesshown in FIGS. 6 and/or 7 . For example, first and second passivebackplanes 420 can be connected to each other via their expansion ports424 as shown in FIGS. 6 or 7 , while the second passive backplane 420can also be connected to a third passive backplane 420 via interconnecttransport cards 418 inserted into the second and third passivebackplanes 420 as shown in FIG. 8 . The approach shown in FIG. 8 canalso be used to couple a passive backplane 420 to multiple other passivebackplanes 420.

The methods and techniques described here may be implemented in digitalelectronic circuitry, or with a programmable processor (for example, aspecial-purpose processor or a general-purpose processor such as acomputer) firmware, software, or in combinations of them. Apparatusembodying these techniques may include appropriate input and outputdevices, a programmable processor, and a storage medium tangiblyembodying program instructions for execution by the programmableprocessor. A process embodying these techniques may be performed by aprogrammable processor executing a program of instructions to performdesired functions by operating on input data and generating appropriateoutput. The techniques may advantageously be implemented in one or moreprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. Generally, aprocessor will receive instructions and data from a read-only memoryand/or a random-access memory. Storage devices suitable for tangiblyembodying computer program instructions and data include all forms ofnon-volatile memory, including by way of example semiconductor memorydevices, such as EPROM, EEPROM, and flash memory devices; magnetic diskssuch as internal hard disks and removable disks; magnetooptical disks;and DVD disks. Any of the foregoing may be supplemented by, orincorporated in, specially-designed application-specific integratedcircuits (ASICs).

A number of embodiments of the invention defined by the following claimshave been described. Nevertheless, it will be understood that variousmodifications to the described embodiments may be made without departingfrom the spirit and scope of the claimed invention. Accordingly, otherembodiments are within the scope of the following claims.

EXAMPLE EMBODIMENTS

Example 1 includes a master unit for a distributed antenna system (DAS)that also includes a plurality of remote antenna units, each remoteantenna unit serving one or more base stations, the master unitcomprising: one or more donor cards, each donor card configured tocouple that donor card to at least one base station; one or moretransport cards, each transport card configured to couple that transportcard to one or more sets of remote antenna units; and at least onepassive backplane, each passive backplane comprising a plurality ofbackplane connectors, wherein each of the backplane connectors isconfigured to connect a respective donor card or transport card to thatpassive backplane, and wherein each of the backplane connectors isconnected to each of the other connectors via one or more respectivepassive bi-directional backplane channels; wherein the master unit isconfigured so that all active processing of streams of digital samplestransported via the DAS is performed by the donor cards and transportcards and not the passive backplane.

Example 2 includes the master unit of Example 1, wherein each of thebackplane connectors is connected to each of the other connectors viaone or more respective fixed passive bi-directional backplane channels.

Example 3 includes the master unit of any of Examples 1-2, wherein theactive processing of the streams of digital samples for the basestations transported via the DAS comprises at least one of: generatingdownlink streams of digital samples for the base stations from downlinkbase station signals received from the base stations; multiplexingindividual downlink streams of digital samples for communication toremote antenna units; receiving uplink streams of digital samples fromremote antenna units; multiplexing individual streams of digital samplesfor communication to individual donor cards or transport cards over thepassive backplane; extracting individual streams of digital samples frommultiplexed streams of digital samples; digitally summing uplink streamsof digital samples for the base stations; and generating uplink basestation signals output to the base stations, the uplink base stationsignals generated from uplink streams of digital samples for the basestations.

Example 4 includes the master unit of any of Examples 1-3, wherein eachdonor card is configured to: for each base station connected to thatdonor card: receive one or more downlink base station signals from thatbase station; and generate one or more downlink streams of digitalsamples for that base station from the one or more downlink base stationsignal received from that base station; for each transport card that iscoupled to one or more remote antenna units that serve one or more ofthe base stations coupled to that donor card: multiplex one or more ofthe downlink streams of digital samples generated by that donor card forcommunication to that transport card; and communicate the multiplexeddownlink streams of digital samples to that transport card via therespective one or more passive backplane channels connected to thebackplane connector used to connect that transport card to therespective passive backplane to which that transport card is connected;receive multiplexed uplink streams of digital samples from thattransport card via the respective one or more passive backplane channelsconnected to the backplane connector used to connect that transport cardto the respective passive backplane to which that transport card isconnected; and extract individual uplink streams of digital samples fromthe multiplexed uplink streams of digital samples received from thattransport card; for each base station connected to that donor card:digitally sum corresponding individual uplink streams of digital samplesfor that base station received via multiple transport cards; andgenerate one or more uplink base station signals for output to that basestation, the one or more uplink base station signals generated from thecorresponding one or more summed uplink streams of digital samples forthe base station.

Example 5 includes the master unit of any of Examples 1-4, wherein eachtransport card is configured to: for each donor card that is connectedto one or more base stations served by one or more of the remote antennaunits coupled to that transport card: receive multiplexed downlinkstreams of digital samples from that donor card via the respective oneor more passive backplane channels connected to the backplane connectorused to connect that donor card to the respective passive backplane towhich that donor card is connected; and extract individual downlinkstreams of digital samples from the multiplexed downlink streams ofdigital samples received from that donor card; and for each set ofremote antenna units coupled to that transport card: multiplex thedownlink streams of digital samples for that set of remote antennaunits; communicate the multiplexed downlink streams of digital samplesto that set of remote antenna units; receive multiplexed uplink streamsof digital samples from that set of remote antenna units; extractindividual uplink streams of digital samples from the multiplexed uplinkstreams of digital samples received from that set of remote antennaunits; and for each base station served by a remote antenna unit coupledto that transport card: digitally sum corresponding individual uplinkstreams of digital samples for that base station received via multipleremote antenna units; and for each donor card that is connected to oneor more base stations served by one or more of the remote antenna unitscoupled to that transport card: multiplex the summed uplink streams ofdigital samples for those one or more base stations for communication tothat donor card; and communicate the multiplexed uplink streams ofdigital samples to that donor card via the respective one or morepassive backplane channels connected to the backplane connector used toconnect that donor card to the respective passive backplane to whichthat donor card is connected.

Example 6 includes the master unit of any of Examples 1-5, wherein eachdonor card comprises a plurality of base station interfaces configuredto couple that donor card to a respective base station.

Example 7 includes the master unit of any of Examples 1-6, wherein eachtransport card comprises a plurality of cable interfaces, each cableinterface configured to couple that transport card to a respective setof remote antenna units.

Example 8 includes the master unit of any of Examples 1-7, wherein atleast one base station comprises a base station configured transmit andreceive an analog downlink RF signal and an analog uplink RF signal; andwherein at least one of the donor cards comprises an RF donor cardcoupled to the base station.

Example 9 includes the master unit of any of Examples 1-8, wherein atleast one base station comprises a baseband unit configured to transmitand receive downlink digital baseband data and uplink digital basebanddata; and wherein at least one of the donor cards comprises a digitaldonor card coupled to the baseband unit.

Example 10 includes the master unit of any of Examples 1-9, wherein eachpassive backplane comprises an expansion port to which each backplaneconnector of that passive backplane is connected via a respective one ormore passive backplane channels; and wherein the expansion port of eachpassive backplane is configured to be coupled to the expansion port ofanother passive backplane.

Example 11 includes the master unit of Example 10, wherein the expansionport of each passive backplane is configured to be coupled to theexpansion port of another passive backplane via a high-speed switchingmatrix.

Example 12 includes the master unit of Example 11, wherein thehigh-speed switching matrix via which two passive backplanes are coupledto each is mounted directly on one of the passive backplanes.

Example 13 includes the master unit of any of Examples 11-12, whereinthe high-speed switching matrix via which two passive backplanes arecoupled to each is mounted to a separate printed circuit board that iscoupled to the expansion ports of the two passive backplanes.

Example 14 includes the master unit of any of Examples 10-13, whereinthe respective expansion port of a first passive backplane is coupled toa respective expansion port of a second passive backplane; and wherein atransport card in the second passive backplane is coupled to a transportcard of a third passive backplane via one or more cables.

Example 15 includes the master unit of any of Examples 1-14, wherein atransport card in a first passive backplane is coupled to a transportcard of a second backplane via one or more cables.

Example 16 includes the master unit of any of Examples 1-15, wherein thetransport cards comprise at least one of: a copper transport cardconfigured to couple copper cables to the master unit; and an opticaltransport card configured to couple optical cables to the master unit.

Example 17 includes the master unit of Example 16, wherein the coppertransport card is configured to provide power to one or more downstreamunits over the copper cables.

Example 18 includes a distributed antenna system (DAS) comprising: amaster unit coupled to one or more base stations; and a plurality ofremote antenna units, each remote antenna unit serving one or more ofthe base stations; wherein the master unit comprises: one or more donorcards, each donor card configured to couple that donor card to at leastone base station; one or more transport cards, each transport cardconfigured to couple that transport card to one or more sets of remoteantenna units; and at least one passive backplane, each passivebackplane comprising a plurality of backplane connectors, wherein eachof the backplane connectors is configured to connect a respective donorcard or transport card to that passive backplane, and wherein each ofthe backplane connectors is connected to each of the other connectorsvia one or more respective passive bi-directional backplane channels;wherein the master unit is configured so that all active processing ofstreams of digital samples transported via the DAS is performed by thedonor cards and transport cards and not the passive backplane.

Example 19 includes the DAS of Example 18, wherein each of the backplaneconnectors is connected to each of the other connectors via one or morerespective fixed passive bi-directional backplane channels.

Example 20 includes the DAS of any of Examples 18-19, wherein the activeprocessing of the streams of digital samples for the base stationstransported via the DAS comprises at least one of: generating downlinkstreams of digital samples for the base stations from downlink basestation signals received from the base stations; multiplexing individualdownlink streams of digital samples for communication to remote antennaunits; receiving uplink streams of digital samples from remote antennaunits; multiplexing individual streams of digital samples forcommunication to individual donor cards or transport cards over thepassive backplane; extracting individual streams of digital samples frommultiplexed streams of digital samples; digitally summing uplink streamsof digital samples for the base stations; and generating uplink basestation signals for output to the base stations, the uplink base stationsignals generated from uplink streams of digital samples for the basestations.

Example 21 includes the DAS of any of Examples 18-20, wherein each donorcard is configured to: for each base station connected to that donorcard: receive one or more downlink base station signals from that basestation; and generate one or more downlink streams of digital samplesfor that base station from the one or more downlink base station signalreceived from that base station; for each transport card that is coupledto one or more remote antenna units that serve one or more of the basestations coupled to that donor card: multiplex one or more of thedownlink streams of digital samples generated by that donor card forcommunication to that transport card; and communicate the multiplexeddownlink streams of digital samples to that transport card via the oneor more respective passive backplane channels connected to the backplaneconnector used to connect that transport card to the respective passivebackplane to which that transport card is connected; receive multiplexeduplink streams of digital samples from that transport card via the oneor more respective passive backplane channels connected to the backplaneconnector used to connect that transport card to the respective passivebackplane to which that transport card is connected; and extractindividual uplink streams of digital samples from the multiplexed uplinkstreams of digital samples received from that transport card; for eachbase station connected to that donor card: digitally sum correspondingindividual uplink streams of digital samples for that base stationreceived via multiple transport cards; and generate one or more uplinkbase station signals for output to that base station, the one or moreuplink base station signals generated from the corresponding one or moresummed uplink streams of digital samples for the base station.

Example 22 includes the DAS of any of Examples 18-21, wherein eachtransport card is configured to: for each donor card that is connectedto one or more base stations served by one or more of the remote antennaunits coupled to that transport card: receive multiplexed downlinkstreams of digital samples from that donor card via the one or morerespective passive backplane channels connected to the backplaneconnector used to connect that donor card to the respective passivebackplane to which that donor card is connected; and extract individualdownlink streams of digital samples from the multiplexed downlinkstreams of digital samples received from that donor card; and for eachset of remote antenna units coupled to that transport card: multiplexthe downlink streams of digital samples for that set of remote antennaunits; communicate the multiplexed downlink streams of digital samplesto that set of remote antenna units; receive multiplexed uplink streamsof digital samples from that set of remote antenna units; extractindividual uplink streams of digital samples from the multiplexed uplinkstreams of digital samples received from that set of remote antennaunits; and for each base station served by a remote antenna unit coupledto that transport card: digitally sum corresponding individual uplinkstreams of digital samples for that base station received via multipleremote antenna units; and for each donor card that is connected to oneor more base stations served by one or more of the remote antenna unitscoupled to that transport card: multiplex the summed uplink streams ofdigital samples for those one or more base stations for communication tothat donor card; and communicate the multiplexed uplink streams ofdigital samples to that donor card via the one or more respectivepassive backplane channels connected to the backplane connector used toconnect that donor card to the respective passive backplane to whichthat donor card is connected.

Example 23 includes the DAS of any of Examples 18-22, wherein each donorcard comprises a plurality of base station interfaces configured tocouple that donor card to a respective base station.

Example 24 includes the DAS of any of Examples 18-23, wherein eachtransport card comprises a plurality of cable interfaces, each cableinterface configured to couple that transport card to a respective setof remote antenna units.

Example 25 includes the DAS of any of Examples 18-24, wherein at leastone base station comprises a base station configured transmit andreceive an analog downlink RF signal and an analog uplink RF signal; andwherein at least one of the donor cards comprises an RF donor cardcoupled to the base station.

Example 26 includes the DAS of any of Examples 18-25, wherein at leastone base station comprises a baseband unit configured to transmit andreceive downlink digital baseband data and uplink digital baseband data;and wherein at least one of the donor cards comprises a digital donorcard coupled to the baseband unit.

Example 27 includes the DAS of Example 18, wherein each passivebackplane comprises an expansion port to which each backplane connectorof that passive backplane is connected via one or more respectivepassive backplane channels; and wherein the expansion port of eachpassive backplane is configured to be coupled to the expansion port ofanother passive backplane.

Example 28 includes the DAS of Example 27, wherein the expansion port ofeach passive backplane is configured to be coupled to the expansion portof another passive backplane via a high-speed switching matrix.

Example 29 includes the DAS of Example 28, wherein the high-speedswitching matrix via which two passive backplanes are coupled to each ismounted directly on one of the passive backplanes.

Example 30 includes the DAS of any of Examples 28-29, wherein thehigh-speed switching matrix via which two passive backplanes are coupledto each is mounted to a separate printed circuit board that is coupledto the expansion ports of the two passive backplanes.

Example 31 includes the DAS of any of Examples 27-30, wherein therespective expansion port of a first passive backplane is coupled to arespective expansion port of a second passive backplane; and wherein atransport card in the second passive backplane is coupled to a transportcard of a third passive backplane via one or more cables.

Example 32 includes the DAS of any of Examples 18-31, wherein atransport card in a first passive backplane is coupled to a transportcard of a second backplane via one or more cables.

Example 33 includes the DAS of any of Examples 18-32, wherein thetransport cards comprise at least one of: a copper transport cardconfigured to couple copper cables to the master unit; and an opticaltransport card configured to couple optical cables to the master unit.

Example 34 includes the DAS of Example 33, wherein the copper transportcard is configured to provide power to one or more downstream units overthe copper cables.

What is claimed is:
 1. A distributed antenna system (DAS) for use withone or more base stations, the DAS comprising: a plurality of remoteantenna units, each remote antenna unit serving one or more of the basestations; one or more donor units, each donor unit configured to couplethe DAS to at least one base station; and one or more transport units,each transport unit configured to couple that transport unit to one ormore sets of remote antenna units, to transmit downlink transportsignals to the one or more sets of remote antenna units, and to receiveuplink transport signals from the one or more sets of remote antennaunits; wherein the DAS is configured to communicatively couple eachdonor unit to at least one of the transport units and to communicativelycouple each transport unit to at least one of the donor units; whereinthe DAS is configured so that all active downlink digital processing forproducing the downlink transport signals transmitted from the transportunits to the remote antenna units is performed by the donor units andthe transport units; and wherein the DAS is configured so that allactive uplink digital processing of the uplink transport signalsreceived by the transport units from the remote antenna units isperformed by the donor units and the transport units.
 2. The DAS ofclaim 1, wherein the active downlink digital processing for producingthe downlink transport signals transmitted from the transport units tothe remote antenna units comprises at least one of: generating downlinkstreams of digital samples for the base stations from downlink basestation signals received from the base stations; and multiplexingindividual downlink streams of digital samples for communication toremote antenna units; and wherein the active uplink digital processingof the uplink transport signals received by the transport units from theremote antenna units comprises at least one of: receiving uplink streamsof digital samples from remote antenna units; multiplexing individualstreams of digital samples for communication to individual donor unitsor transport units; extracting individual streams of digital samplesfrom multiplexed streams of digital samples; digitally summing uplinkstreams of digital samples for the base stations; and generating uplinkbase station signals for output to the base stations, the uplink basestation signals generated from uplink streams of digital samples for thebase stations.
 3. The DAS of claim 1, wherein each donor unit isconfigured to: for each base station connected to that donor unit:receive one or more downlink base station signals from that basestation; and generate one or more downlink streams of digital samplesfor that base station from the one or more downlink base station signalreceived from that base station; for each transport unit that is coupledto one or more remote antenna units that serve one or more of the basestations coupled to that donor unit: multiplex one or more of thedownlink streams of digital samples generated by that donor unit forcommunication to that transport unit; and communicate the multiplexeddownlink streams of digital samples to that transport unit; receivemultiplexed uplink streams of digital samples from that transport unit;and extract individual uplink streams of digital samples from themultiplexed uplink streams of digital samples received from thattransport unit; for each base station connected to that donor unit:digitally sum corresponding individual uplink streams of digital samplesfor that base station received via multiple remote antenna units; andgenerate one or more uplink base station signals for output to that basestation, the one or more uplink base station signals generated from thecorresponding one or more summed uplink streams of digital samples forthe base station.
 4. The DAS of claim 1, wherein each transport unit isconfigured to: for each donor unit that is connected to one or more basestations served by one or more of the remote antenna units coupled tothat transport unit: receive multiplexed downlink streams of digitalsamples from that donor unit; and extract individual downlink streams ofdigital samples from the multiplexed downlink streams of digital samplesreceived from that donor unit; and for each set of remote antenna unitscoupled to that transport unit: multiplex the downlink streams ofdigital samples for that set of remote antenna units; communicate themultiplexed downlink streams of digital samples to that set of remoteantenna units; receive multiplexed uplink streams of digital samplesfrom that set of remote antenna units; extract individual uplink streamsof digital samples from the multiplexed uplink streams of digitalsamples received from that set of remote antenna units; and for eachbase station served by a remote antenna unit coupled to that transportunit: digitally sum corresponding individual uplink streams of digitalsamples for that base station received via multiple remote antennaunits; and for each donor unit that is connected to one or more basestations served by one or more of the remote antenna units coupled tothat transport unit: multiplex the summed uplink streams of digitalsamples for those one or more base stations for communication to thatdonor unit; and communicate the multiplexed uplink streams of digitalsamples to that donor unit.
 5. The DAS of claim 1, wherein each donorunit comprises a plurality of base station interfaces configured tocouple that donor unit to a respective base station.
 6. The DAS of claim1, wherein each transport unit comprises a plurality of cableinterfaces, each cable interface configured to couple that transportunit to a respective set of remote antenna units.
 7. The DAS of claim 1,wherein at least one base station comprises a base station configuredtransmit and receive an analog downlink RF signal and an analog uplinkRF signal; and wherein at least one of the donor units comprises an RFdonor unit coupled to the base station.
 8. The DAS of claim 1, whereinat least one base station comprises a baseband unit configured totransmit and receive downlink digital baseband data and uplink digitalbaseband data; and wherein at least one of the donor units comprises adigital donor unit coupled to the baseband unit.
 9. The DAS of claim 1,wherein the transport units comprise at least one of: a copper transportunit configured to communicate with a set of remote antenna units usingcopper cables; and an optical transport unit configured to communicatewith a set of remote antenna units using optical cables.
 10. The DAS ofclaim 9, wherein the copper transport unit is configured to providepower to one or more downstream units over the copper cables.
 11. TheDAS of claim 1, wherein the DAS further comprises a passive backplane.12. A master unit for a distributed antenna system (DAS) that alsoincludes a plurality of remote antenna units, each remote antenna unitserving one or more base stations, the master unit comprising: one ormore donor cards, each donor card configured to couple that donor cardto at least one base station; and one or more transport cards, eachtransport card configured to couple that transport card to one or moresets of remote antenna units; and wherein the master unit is configuredto communicatively couple each donor card to at least one of thetransport cards and to communicatively couple each transport card to atleast one of the donor cards; wherein the master unit is configured sothat all active downlink digital processing for producing the downlinktransport signals transmitted from the transport units to the remoteantenna units is performed by the donor units and the transport units;and wherein the master unit is configured so that all active uplinkdigital processing of the uplink transport signals received by thetransport units from the remote antenna units is performed by the donorunits and the transport units.
 13. The master unit of claim 12, whereinthe active downlink digital processing for producing the downlinktransport signals transmitted from the transport units to the remoteantenna units comprises at least one of: generating downlink streams ofdigital samples for the base stations from downlink base station signalsreceived from the base stations; and multiplexing individual downlinkstreams of digital samples for communication to remote antenna units;and wherein the active uplink digital processing of the uplink transportsignals received by the transport units from the remote antenna unitscomprises at least one of: receiving uplink streams of digital samplesfrom remote antenna units; multiplexing individual streams of digitalsamples for communication to individual donor units or transport units;extracting individual streams of digital samples from multiplexedstreams of digital samples; digitally summing uplink streams of digitalsamples for the base stations; and generating uplink base stationsignals for output to the base stations, the uplink base station signalsgenerated from uplink streams of digital samples for the base stations.14. The master unit of claim 12, wherein each donor card is configuredto: for each base station connected to that donor card: receive one ormore downlink base station signals from that base station; and generateone or more downlink streams of digital samples for that base stationfrom the one or more downlink base station signal received from thatbase station; for each transport card that is coupled to one or moreremote antenna units that serve one or more of the base stations coupledto that donor card: multiplex one or more of the downlink streams ofdigital samples generated by that donor card for communication to thattransport card; and communicate the multiplexed downlink streams ofdigital samples to that transport card; receive multiplexed uplinkstreams of digital samples from that transport card; and extractindividual uplink streams of digital samples from the multiplexed uplinkstreams of digital samples received from that transport card; for eachbase station connected to that donor card: digitally sum correspondingindividual uplink streams of digital samples for that base stationreceived via multiple remote antenna units; and generate one or moreuplink base station signals for output to that base station, the one ormore uplink base station signals generated from the corresponding one ormore summed uplink streams of digital samples for the base station. 15.The master unit of claim 12, wherein each transport card is configuredto: for each donor card that is connected to one or more base stationsserved by one or more of the remote antenna units coupled to thattransport card: receive multiplexed downlink streams of digital samplesfrom that donor card; and extract individual downlink streams of digitalsamples from the multiplexed downlink streams of digital samplesreceived from that donor card; and for each set of remote antenna unitscoupled to that transport card: multiplex the downlink streams ofdigital samples for that set of remote antenna units; communicate themultiplexed downlink streams of digital samples to that set of remoteantenna units; receive multiplexed uplink streams of digital samplesfrom that set of remote antenna units; extract individual uplink streamsof digital samples from the multiplexed uplink streams of digitalsamples received from that set of remote antenna units; and for eachbase station served by a remote antenna unit coupled to that transportcard: digitally sum corresponding individual uplink streams of digitalsamples for that base station received via multiple remote antennaunits; and for each donor card that is connected to one or more basestations served by one or more of the remote antenna units coupled tothat transport card: multiplex the summed uplink streams of digitalsamples for those one or more base stations for communication to thatdonor card; and communicate the multiplexed uplink streams of digitalsamples to that donor card.
 16. The master unit of claim 12, whereineach donor card comprises a plurality of base station interfacesconfigured to couple that donor card to a respective base station. 17.The master unit of claim 12, wherein each transport card comprises aplurality of cable interfaces, each cable interface configured to couplethat transport card to a respective set of remote antenna units.
 18. Themaster unit of claim 12, wherein at least one base station comprises abase station configured transmit and receive an analog downlink RFsignal and an analog uplink RF signal; and wherein at least one of thedonor cards comprises an RF donor card coupled to the base station. 19.The master unit of claim 12, wherein at least one base station comprisesa baseband unit configured to transmit and receive downlink digitalbaseband data and uplink digital baseband data; and wherein at least oneof the donor cards comprises a digital donor card coupled to thebaseband unit.
 20. The master unit of claim 12, wherein the transportcards comprise at least one of: a copper transport card configured tocouple copper cables to the master unit; and an optical transport cardconfigured to couple optical cables to the master unit.
 21. The masterunit of claim 20, wherein the copper transport card is configured toprovide power to one or more downstream units over the copper cables.22. The master unit of claim 12, wherein the master unit furthercomprises a passive backplane.
 23. A method for use with a distributedantenna system (DAS) and one or more base stations served by the DAS,the method comprising: communicatively coupling each of one or moredonor units of the DAS to at least one base station; communicativelycoupling each of one or more transport units of the DAS to one or moresets of remote antenna units; communicatively coupling each donor unitto at least one of the transport units; communicatively coupling eachtransport unit to at least one of the donor units; performing, by thedonor units and the transport units, all active downlink processing forproducing the downlink transport signals transmitted from the transportunits to the remote antenna units; and performing, by the donor unitsand the transport units, all active uplink processing of the uplinktransport signals received by the transport units from the remoteantenna units.
 24. The method of claim 23, wherein the active downlinkdigital processing for producing the downlink transport signalstransmitted from the transport units to the remote antenna unitscomprises at least one of: generating downlink streams of digitalsamples for the base stations from downlink base station signalsreceived from the base stations; and multiplexing individual downlinkstreams of digital samples for communication to remote antenna units;and wherein the active uplink digital processing of the uplink transportsignals received by the transport units from the remote antenna unitscomprises at least one of: receiving uplink streams of digital samplesfrom remote antenna units; multiplexing individual streams of digitalsamples for communication to individual donor units or transport units;extracting individual streams of digital samples from multiplexedstreams of digital samples; digitally summing uplink streams of digitalsamples for the base stations; and generating uplink base stationsignals for output to the base stations, the uplink base station signalsgenerated from uplink streams of digital samples for the base stations.25. The method of claim 23, wherein each donor unit is configured to:for each base station connected to that donor unit: receive one or moredownlink base station signals from that base station; and generate oneor more downlink streams of digital samples for that base station fromthe one or more downlink base station signal received from that basestation; for each transport unit that is coupled to one or more remoteantenna units that serve one or more of the base stations coupled tothat donor unit: multiplex one or more of the downlink streams ofdigital samples generated by that donor unit for communication to thattransport unit; and communicate the multiplexed downlink streams ofdigital samples to that transport unit; receive multiplexed uplinkstreams of digital samples from that transport unit; and extractindividual uplink streams of digital samples from the multiplexed uplinkstreams of digital samples received from that transport unit; for eachbase station connected to that donor unit: digitally sum correspondingindividual uplink streams of digital samples for that base stationreceived via multiple remote antenna units; and generate one or moreuplink base station signals for output to that base station, the one ormore uplink base station signals generated from the corresponding one ormore summed uplink streams of digital samples for the base station. 26.The method of claim 23, wherein each transport unit is configured to:for each donor unit that is connected to one or more base stationsserved by one or more of the remote antenna units coupled to thattransport unit: receive multiplexed downlink streams of digital samplesfrom that donor unit; and extract individual downlink streams of digitalsamples from the multiplexed downlink streams of digital samplesreceived from that donor unit; and for each set of remote antenna unitscoupled to that transport unit: multiplex the downlink streams ofdigital samples for that set of remote antenna units; communicate themultiplexed downlink streams of digital samples to that set of remoteantenna units; receive multiplexed uplink streams of digital samplesfrom that set of remote antenna units; extract individual uplink streamsof digital samples from the multiplexed uplink streams of digitalsamples received from that set of remote antenna units; and for eachbase station served by a remote antenna unit coupled to that transportunit: digitally sum corresponding individual uplink streams of digitalsamples for that base station received via multiple remote antennaunits; and for each donor unit that is connected to one or more basestations served by one or more of the remote antenna units coupled tothat transport unit: multiplex the summed uplink streams of digitalsamples for those one or more base stations for communication to thatdonor unit; and communicate the multiplexed uplink streams of digitalsamples to that donor unit.
 27. The method of claim 23, wherein eachdonor unit comprises a plurality of base station interfaces configuredto couple that donor unit to a respective base station.
 28. The methodof claim 23, wherein each transport unit comprises a plurality of cableinterfaces, each cable interface configured to couple that transportunit to a respective set of remote antenna units.
 29. The method ofclaim 23, wherein at least one base station comprises a base stationconfigured transmit and receive an analog downlink RF signal and ananalog uplink RF signal; and wherein at least one of the donor unitscomprises an RF donor unit coupled to the base station.
 30. The methodof claim 23, wherein at least one base station comprises a baseband unitconfigured to transmit and receive downlink digital baseband data anduplink digital baseband data; and wherein at least one of the donorunits comprises a digital donor unit coupled to the baseband unit. 31.The method of claim 23, wherein the transport units comprise at leastone of: a copper transport unit configured to communicate with a set ofremote antenna units using copper cables; and an optical transport unitconfigured to communicate with a set of remote antenna units usingoptical cables.
 32. The method of claim 31, wherein the copper transportunit is configured to provide power to one or more downstream units overthe copper cables.
 33. The method of claim 23, wherein communicativelycoupling each donor unit to at least one of the transport unitscomprises communicatively coupling each donor unit to at least one ofthe transport units using a passive backplane; and whereincommunicatively coupling each transport unit to at least one of thedonor units comprises communicatively coupling each transport unit to atleast one of the donor units using the passive backplane.